This is where the Perl compiler becomes your best friend. If you run perl -MO=Deparse,-p [your script name here], the presedence Perl sees will be printed out. See below for your code example from above, which I stored in hello.pl.

    [cmilfo@cmilfo monks]$ perl -MO=Deparse,-p hello.pl

    ($nice = 0);
    sub hello1 {
        (($nice or return('Hi')) or return('Get Lost!'));
    }
    sub hello2 {
        (((!$nice) || return('Hi')) and return('Get Lost!'));
    }
    print(hello1(), hello2());
    hello.pl syntax OK
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It basically puts in all the () and {} that we may not see.

Cheers!
Casey